Cast cutter



Jan." 11, 1955 c. G. A. me UAL CAST CUTTER Filed July Vs, 1952 5 rHN@ ,e ma. m v.J w64 4 5w, /MW a a@ United States Patent O CAST CUTTER Charles George Albert King, Carshalton, and Reginald .lames Norris, Sutton, England; Sophia King, executrix of said Charles George Albert King, deceased Application July 3, 1952, Serial No. 297,092

1i) Claims. (Cl. 311-166) This invention relates to cast-cutters for the removal of plaster casts, bandages and the like, with or without felt or like padding and with or without reinforcements. For this purpose, it is usual for the cast or bandage to be divided up into sections which can be removed individually from place with the least inconvenience to the patient; such devices may be of service also for trimming a cast or bandage after application, as by the removal of superfluous portions, for example in order to reduce discomfort to the patient while the cast or bandage remains in place, or for cutting apertures at desired points of a cast or bandage, or again for trimming beds of plaster.

The invention has for its main object to provide an improved device for these purposes, in the form of a portable and electrically operated tool of low weight, capable of dealingwith casts or bandages of varying thicknesses, even when covered with plastic or textile material and reinforced by libres or wires. Another object is to enable the tool to follow a curved cutting line when desired; furthermore, particular attention is given to the question of electrical insulation so as to guard against the danger of shock to the operator or the patient, arising from the use of an electric motor combined with the cutting tool.

Other objects and advantages of the invention will hereinafter appear from the following description of a preferred embodiment, given with reference to the accompanying drawings, in which:

Fig. l is an elevation of the complete apparatus partly in section to reveal the internal arrangement.

Pig. 2 is a part elevation, showing the cutting tool in operation.

Fig. 3 is a cross section on the line 3-3 of Fig. 1.

Fig. 4 is a detail in cross section on the line 4--4 of Fi l.

leferring to Fig. l, the apparatus comprises a lightweight electric motor M with enclosed reducing gear, such as employed for small portable drills, the motor housing being formed with a pistol-grip handle which carries a switch trigger 11 having a locking button 12, as well known in the electrical art. The handle 10 is preferably made of insulating material for the greater safety of the operator.

At the other end of the motor housing, from which the drive is taken olf, as by means of a bevel gear upon the powershaft 24, there is secured a substantially rectanguiar casing 13, made of light alloy or of plastic material and provided with a detachable cover plate 14 fitting into a rabbet 25 upon one face of the casing; behind the cover plate there is a recess 15 enclosing the cutting tool, which is preferably a saw 16 of the endless chain type, driven by a sprocket 17 near the upper end of the casing, this sprocket being connected to a gear meshing with that upon the powershaft. The lower portion of the chain is supported by an arm 18 adjustably mounted in the rear wall of the recess 15, as by a screw 19, the arm projecting from the open lower end of the casing and having its extremity 20 rounded for easy passage of the chain saw. The chain is guided by a tracking rib 21 extending along the sides of the arm and around its extremity 20, the links rubbing against the rib 21 with very slight friction except at the extremity 20; thus it will not be necessary to provide lubricant, any wear at the extremity 20 being compensated by adjusting the arm 18 downwards of the recess 15. The chain is provided with cutting teeth 22 formed on the exterior edges of the links; these teeth are preferably staggered on alternate links, as shown.

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The casing 13 is formed with two parallel bores 28, 29, on either side of the recess 15, within which there are slidable two parallel tubular members 30, 31, connected at their lower ends by a cross-beam 32; the latter carries two vertical webs 33, 34, extending up inside the recess 15, one in front of the chain saw 16 and the other behind it in a deepened portion of the recess. The movement of the cross-beam is limited by a screw 27 fixed in the arm 18, with its point engaging in a vertical slot in the rear web 34. The cross-beam 32 and its webs 33, 34 form a guard for the chain saw, of which only the lower portion projecting through a central slot 26 in the beam will be exposed; the tubular members 30, 31 are normally forced downwards in the bores 28, 29, by the action of coiled springs 35, 36 pressing down upon their upper extremities inside the bores.

A guide 37 is slidable within the tubular member 30, being normally urged downwards by an inner coiled spring 38 fitting inside the hollow upper end of the guide within the bore 28; the solid lower end 39 of this guide projects below the cross-beam 32 and is cranked towards the chain saw, its extremity 49 being formed as a foot which is designed to be interposed between the bottom run of the chain saw 16 and the surface of the patients skin, so as to avoid any danger of injury to the patient by the cutting teeth 22.

The upper surface of the foot or extremity 40 is recessed as at 41 to accommodate the lower run of the chain saw when the foot 40 is raised towards the casing 13 against the action of the spring 38; lifting of the guide foot is effected by means of a lever 42 pivoted at 43 upon the pistol-grip handle 10, the lever being engageable by a hand grasping the handle, and a second arm 44 of this lever being adapted to engage in a notch 45 formed in the guide 37, passing freely through slots 46, 47 provided respectively in the tubular member 30 and in the wall of the bore 28. The lever 42, the guiding foot 40 and the cranked portion 39 are preferably insulated, as by layers of plastic material 48, as an additional safeguard against electric shock to the operator and patient; the cranked portion 39 is also preferably stream-lined or tapered in cross-section, as seen in Fig. 4, to a width slightly less than the thickness of the chain saw, so as to facilitate the cutting of a cast or bandage along curved lines, if so desired, the major axis of the cross-section being in the central plane of the chain saw.

A hollow presser 49 arranged in a similar way inside the other tubular member 3l, and normally urged down by an inner coiled spring 50 pressing inside it within the bore 29, is provided at its lower extremity with a foot 51 which will rest upon the surface of a cast or bandage which is being cut by the chain saw, as shown in Fig. 2; the foot 51 can enter the slot 26 in the lower face of the cross-beam 32, and a linger-hold 52 is provided for lifting the presser foot if necessary.

In order to prevent the twisting of this foot, the presser 49 is formed with a rib or key 53 engaging in a slot or keyway 54 cut in the member 31.

ln operation, the pistol-grip handle lil will be grasped by one hand and the presser foot 51 will be lifted either by resting it upon the plaster or by means of the lingerhold 52, using the other hand. With the presser foot in this raised position, the operator will then allow the guide foot 4t) to slide gently over the patients arm or other part of the body, and will insinuate it beneath the plaster cast or bandage. Then by pressing the lever 42, and thereby allowing the whole device to descend towards the foot 4t), which is retained .under the plaster, he will bring the cross-beam 32 down upon the outer surface of the cast or bandage; further pressure upon the lever 42 will again allow the device to descend towards the foot 40, except that the cross-beam 32 will be held up by its contact with the outer surface of the bandage. The relative motion between the cross-beam and the remainder of the device will cause the lower end of the chain saw 16 and the extremity of the arm 1S to emerge through the slot 26 in the middle of the cross-beam, the sawteeth 22 quickly cutting down into the plaster under the pressure exerted through the lever 42, as soon as the motor is started. When the saw has cut right through to the inner surface of the bandage B, as indicated in Fig. 2, its teeth will enter into the recess 41 on the upper surface of the foot 40, which will shield them from any possibility of cutting the patients arm A; the operator can then extend the cut in the desired direction, towards the left as viewed in Fig. 2, by moving the device accordingly. The teeth 22 on the down run of the chain saw will act to cut away the plaster for the entire thickness of the bandage B, so long as the lever 42 is grippedto keep the guide foot 40 in its fully raised position relative to the casing 13, while the presser foot 51 and the crossbeam 32 will rest upon the outer surface of the bandage under the action of their springs, adapting themselves to any change of thickness of the plaster. Upon completion of the cut, the lever 42 can be released, and the motor switched off by means of the button 12.

It will be noted that the stream-line or tapered crosssection given to the guide at its lower end 39, adjacent to the foot 40, enables the operator to steer the device around the curves in making the cut; thus the plaster cut can be divided into sections of desired shapes to facilitate removal of the whole or part, or to su1t the particular pattern of cast at an elbow, knee, ankle or other joint or at any other part of the body. The device will cut plaster of any thickness within the capacity of the tool, up to a maximum represented by the projection of the chain saw 16 beyond the cross-beam 32 when the latter is forced back against the casing 13; evidently this capacity may be increased by substituting a longer run of chain and adjusting the arm 18 or fitting a longer arm, as may be desired.

Electric motors such as will be employed in devices of this kind are normally constructed with adequate insulation to prevent leakage of current to the frame, shaft and other exposed parts, but even with this insulation unimpaired, it may happen that absolute security against electric shock will depend upon the position of a switch, the correct iitting of a plug connector into its socket, and other circumstances of which the user of the apparatus may well be unaware.

In the present instance, the electric motor driving the device is provided with double insulation, that is to say that the motor M has its frame or housing, the power shaft 24 and any exposed parts properly insulated from the electrical supply circuit according to normal practice, and further, the handle insulates the operator from the motor housing; the lever 42 is also insulated so that there is no danger of shock to the operator. Consequently, any accidental connection of the normally insulated parts of the motor to the supply circuit, as by failure of their insulation, or the reverse-fitting of a plug connector whereby the normally live parts of the motor are grounded and the positive pole of the supply circuit is connected to the normally grounded parts of the motor, cannot result in leakage through the operators handle 10 or lever 42. In addition, the guiding foot 40 is protected by the insulating layer 48 which is the only surface actually making contact with the patients body. These precautions are not only necessary in order to prevent the possibility of electric shock, but also desirable in order to establish the patients confidence that he will not suffer by the use of an electrically driven device.

Moreover, the chain saw is enclosed in the casing 13 and guarded by the slotted cross-beam 32 so that no moving part of the chain will normally be visible, the lower run exposed by movement of the guard cross-beam 32 being wholly within the thickness of the bandage; there is therefore no danger of injury or damage by the operation of the chain saw, even if the device is handled carelessly.

The same motor M may be employed for driving a fan to exhaust air from the vicinity of the tool so as to draw off the dust produced by the cutting of the plaster, a flexible or other pipe being provided for discharging such dust-laden air clear of the device, for example into a flexible bag such as employed for vacuum-cleaning appliances.

What we claim is:

1. Cast-cutter comprising a cutting tool, a casing for said tool, said tool having an operative part projecting from said casing, a guard slidably mounted on said casing and adapted to shield the projecting operative part of said tool, a guide slidably mounted on said casing, said guide including a foot adapted for insertion beneath a cast to be removed from a patient, and manual means for controlling movement of said guide in relation to said casing, approach of said casing to said guide automatically bringing said guard into contact with said cast, and approach of said guide to said casing causing said cast to push back said guard and expose the operative part of said tool for cutting said cast.

2. Cast-cutter comprising a cutting tool, a casing for said tool, said tool having an operative part projecting from said casing, a guard slidably mounted on said casing and adapted to shield the projecting operative part of said tool, a guide slidably mounted on said casing, said guide including a foot adapted for insertion beneath a cast to be removed from a patient, a presser slidably mounted on said casing, said presser including a foot adapted to rest on the outer surface of said cast, and manual means for controlling movement of said guide in relation to said casing, approach of said casing to said guide bringing said guard and said presser into contact with said cast, and approach of said guide to said carrier causing said cast to push back said guard and said presser and expose the operative part of said tool for cutting said cast.

3. Cast-cutter comprising a cutting tool, a casing for said tool, said tool having an operative part projecting from said casing, a guard slidably mounted on said casing and adapted to shield the projecting operative part of said tool, a guide slidably mounted on said casing, said guide including a foot adapted for insertion beneath a cast to be removed from a patient, manual means for supporting said casing, motor and driving means, and associated manual means for controlling said motor and for controlling movement of said guide in relation to said casing, approach of said casing to said guide automatically bringing said guard into contact with said cast, and approach of said guide to said casing causing said cast to push back said guard and expose the operative part of said tool for cutting said cast.

4. Cast-cutter comprising an endless chain saw, a casing for said saw, said saw having an operative part projecting from said casing, a guard slidably mounted on said casing and adapted to shield the projecting operative part of said saw, a guide slidably mounted on said casing, said guide including a foot adapted for insertion beneath a cast to be removed from a patient, and manual means for controlling movement of said guide in relation to said casing, approach of said casing to said guide automatically bringing said guard into contact with said cast, and approach of said guide to said casing causing said cast to push back said guard and expose the operative part of said saw for cutting said cast.

5. Castcutter comprising a cutting tool, a casing for said tool, said tool having an operative part projecting from said casing, a guard slidably mounted on said casing and adapted to shield the projecting operative part of said tool, a guide slidably mounted on said casing and including a foot adapted for insertion beneath a cast to be removed from a patient, a presser slidably mounted on said casing and including a foot adapted to rest on the outer surface of said cast, and manual means for controlling movement of said guide in relation to said casing.

6. In a device of the class described, a cutting tool consisting of an endless chain saw, a casing for said saw, said saw having an operative part projecting from said casing, a guard slidably mounted in said casing and adapted to shield the projecting operative part of said saw, a guide slidably mounted in said casing and including a foot adapted for insertion beneath a cast to be removed from a patient, a presser slidably mounted in said casing and including a foot adapted to rest on the outer surface of said cast, said guide and said presser being mounted for parallel sliding movement on opposite sides of said saw and in its plane of operation, and said guard being mounted between said slide and presser for sliding movement parallel thereto, and manual means for controlling movement of said guide in relation to said casing, approach of said casing to said guide bringing said guard and said presser into contact with the outer surface of said cast, and approach of said guide to said casing causing said cast to push back said guard and said presser and expose the operative part of said saw for cutting said cast.

7. In a device of the class described, a cutting tool consisting of an endless chain saw, a casing for said saw, said saw having an operative part projecting from said casing, a guard slidably mounted in said casing and adapted to shield the projecting operative part of said saw, a guide slidably mounted in said casing and including a foot adapted for insertion beneath a cast to be removed from a patient, said guard and said guide being mounted for parallel sliding movement in the plane of operation of said saw, said guard including two parallel webs lying parallel to said plane and on opposite faces of said saw, said guide including a member lying in said plane and on one side of said saw, and manual means for controlling movement of said guide in relation to said casing, said guard normally resting upon the outer surface of said cast with its Webs shielding the faces of said saw, and approach of said guide to said casing causing said cast to push back said guard and expose the operative part of said saw for cutting said cast.

8. In a device of the class described, the combination of a cutting tool consisting of an endless chain saw, a casing for said saw, said saw having an operative part projecting from said casing, a guard slidably mounted in said casing, and adapted to shield the projecting operative part of said saw, a guide slidably mounted in said casing and including a foot adapted for insertion beneath a cast to be removed from a patient, said guide foot having a recess upon its face contacting with said cast, and manual means for controlling movement of said guide in relation to said casing, approach of said casing to said guide bringing said guard into contact with the outer surface of said cast, and approach of said guide to said casing causing said cast to push back said guard and expose the operative part of said saw for cutting said cast, said operative part at its maximum exposure being accommodated in said recess.

9. In a device of the class described, a cutting tool consisting of an endless chain saw, a casing for said saw, said saw having an operative part projecting from said casing, a guard slidably mounted in said casing and adapted to shield the projecting operative part of said saw, said guard comprising two Webs located respectively in front of and behind said saw and extending partly inside said casing, and a cross-beam connected to the ends of said webs, said cross-beam being slotted for passage of the projecting operative part of said saw, a guide slidably mounted in said casing and including a limb terminating in a foot adapted for insertion beneath a cast to be removed from a patient, part of said limb adjacent to said foot having a tapered cross-section of less Width than said saw, and manual means for controlling movement of said guide in relation to said casing, approach of said casing to said guide bringing said guard into contact with the outer surface of said cast, and approach of said guide to said casing causing said cast to push back said guard and expose the operative part of said saw for cutting said cast.

l0. Cast cutter comprising a cutting tool, an elongated casing for said tool, said tool having an operative part projecting from said casing, a guard slidably mounted cn said casing and adapted to shield the projecting operative part of said tool, a guide slidably mounted on said casing, said guide including a foot adapted for insertion beneath a cast to be removed from a patient, manual means for controlling movement of said guide in relation to said casing, approach of said casing to said guide automatically bringing said guard into contact with said cast, and approach of said guide to said casing causing said cast to push back said guard and expose the operative part of said tool for cutting said cast, and a handle rigidly connected at one end to said casing, said handle extending longitudinally in spaced side-by-side relationship to said casing and pivotally supporting said manual control means, said manual control means consisting of a first arm engaging said guide and a second arm located between said handle and casing, said second arm being operable to cause said rst arm to move said guide relatively to said casing.

References Cited in the file of this patent UNITED STATES PATENTS 1,948,109 Hager Feb. 20, 1934 1,951,880 Niederhofer Mar. 20, 1934 2,291,470 Hope July 28, 1942 2,492,156 Kupjack Dec. 27, 1949 FOREIGN PATENTS 698,743 Germany Nov. 16, 1940 

